This study concerns the production of pituitary hormones, specifically Human Growth Hormone and Prolactin as well as cortisol, in relationship to sleep and various aspects of the sleep-waking cycle. The experimental technique used is 24-hour polygraphic monitoring of sleep-waking cycles along with frequent blood sampling (every twenty minutes) over the same time period. Various patient groups, having either endocrinological or neurological disorders are investigated as well as the effects of manipulation of the sleep-waking cycle on normal adults' hormone release.